\begin{table}[htbp!] \centering \footnotesize \begin{threeparttable} \caption{Sample characteristics} \begin{tabular} {l c c c c c c c} \toprule & Overall & \multicolumn{2}{c}{Effect size{$>$}median} & \multicolumn{2}{c}{City staff retained} & \multicolumn{2}{c}{Comm. pre-existed} \\ \cmidrule(lr){2-2} \cmidrule(lr){3-4} \cmidrule(lr){5-6} \cmidrule(lr){7-8} Frequency in category (\%) & (1) & (2) No & (3) Yes & (4) No & (5) Yes & (6) No & (7) Yes \\ \hline  \multicolumn{8}{l}{\textit{Nudge effectiveness}} \\ %
\hspace{1em}Max $ t{\geq}1.96$ & 45.21 & 21.62 & 69.44* & 44.44 & 45.65 & 44.23 & 47.62 \\
\hspace{1em}Max treatment effect $\geq 1$ pp. & 46.58 & 0.00 & 94.44* & 40.74 & 50.00 & 42.31 & 57.14 \\ \\ \multicolumn{8}{l}{\textit{Organizational features}} \\ %
\hspace{1em}City certified by What Works Cities & 60.27 & 64.86 & 55.56 & 62.96 & 58.70 & 63.46 & 52.38 \\
\hspace{1em}City staff member from trial retained & 63.01 & 59.46 & 66.67 & 0.00 & 100.00* & 59.62 & 71.43 \\
\hspace{1em}Partner city dept. in charge of implementing & 79.45 & 75.68 & 83.33 & 85.19 & 76.09 & 75.00 & 90.48 \\
\hspace{1em}Senior city staff on trial (Director/Chief) & 53.42 & 56.76 & 50.00 & 48.15 & 56.52 & 61.54 & 33.33* \\ \\ \multicolumn{8}{l}{\textit{Experimental design}} \\ %
\hspace{1em}Communication pre-existed before trial & 28.77 & 21.62 & 36.11 & 22.22 & 32.61 & 0.00 & 100.00* \\
\hspace{1em}Nudge communication uses Simplification & 53.42 & 48.65 & 58.33 & 59.26 & 50.00 & 44.23 & 76.19* \\
\hspace{1em}Nudge communication uses Personal Motivation & 57.53 & 56.76 & 58.33 & 70.37 & 50.00 & 61.54 & 47.62 \\
\hspace{1em}Nudge communication uses Social Cues & 56.16 & 59.46 & 52.78 & 51.85 & 58.70 & 55.77 & 57.14 \\ \\ \multicolumn{8}{l}{\textit{Policy area}} \\ %
\hspace{1em}Revenue collection \& debt repayment & 24.66 & 16.22 & 33.33 & 29.63 & 21.74 & 17.31 & 42.86 \\
\hspace{1em}Registration \& regulation compliance & 20.55 & 13.51 & 27.78 & 14.81 & 23.91 & 19.23 & 23.81 \\
\hspace{1em}Workforce \& education & 20.55 & 29.73 & 11.11 & 25.93 & 17.39 & 23.08 & 14.29 \\
\hspace{1em}Take-up of benefits and programs & 13.70 & 16.22 & 11.11 & 11.11 & 15.22 & 15.38 & 9.52 \\
\hspace{1em}Community engagement & 13.70 & 18.92 & 8.33 & 11.11 & 15.22 & 17.31 & 4.76 \\
\hspace{1em}Health & 5.48 & 5.41 & 5.56 & 7.41 & 4.35 & 5.77 & 4.76 \\
\hspace{1em}Environment & 1.37 & 0.00 & 2.78 & 0.00 & 2.17 & 1.92 & 0.00 \\ \\ \multicolumn{8}{l}{\textit{Medium}} \\ %
\hspace{1em}Physical letter & 38.36 & 29.73 & 47.22 & 51.85 & 30.43 & 25.00 & 71.43* \\
\hspace{1em}Email & 30.14 & 27.03 & 33.33 & 22.22 & 34.78 & 32.69 & 23.81 \\
\hspace{1em}Postcard & 21.92 & 27.03 & 16.67 & 22.22 & 21.74 & 30.77 & 0.00* \\
\hspace{1em}Text message & 10.96 & 10.81 & 11.11 & 3.70 & 15.22 & 11.54 & 9.52 \\
\hspace{1em}Website & 4.11 & 5.41 & 2.78 & 0.00 & 6.52 & 3.85 & 4.76 \\ \hline
Number of trials & 73 & 37 & 36 & 27 & 46 & 52 & 21 \\
\bottomrule \end{tabular} \label{tab:sumstats} \begin{tablenotes} \scriptsize \item This table shows the frequencies of trials for each category listed in the leftmost column. Column 1 shows the frequences for all trials. Columns 2 and 3 partition the sample along the median of the maximum effect size in each trial. Columns 4 and 5 consider separately trials for which all the city collaborators from the trial have departed versus trials that have at least one original staff member still working in the same city department. Columns 6 and 7 distinguish between trials that tested nudges in a new communication and those that added nudges to a pre-existing communication that the city had been sending before the trial. \item *Asterisk indicates that the $ p\text{-value}$ of the difference{$<$}0.05. Standard errors are clustered by city. Except when there are fewer than 5 trials in one of the $ 2{\times}2$ cells, $ p\text{-values}$ are calculated using the two-sided Fisher's exact test instead. \end{tablenotes} \end{threeparttable} \end{table}
